In forming a buildup type multilayer printed wiring board constituting an IC chip package, interlayer insulating resin is formed on one of or each of the surfaces of a core substrate having through holes formed therein and via holes for interlayer conduction are opened by a laser or photo etching, whereby an interlayer resin insulating layer is thereby formed. A conductor layer is formed on the via holes by plating or the like and etching and the like are performed to form a pattern, thus creating a conductor circuit. Further, by repeatedly forming the interlayer insulating layer and the conductor layer, the buildup multilayer printed wiring board is obtained. By forming solder bumps and external terminals (PGA/BGA's or the like) on the front layer of the board at need, the board becomes a substrate capable of mounting an IC chip thereon or a package substrate. The IC chip is C4 (flip-chip) mounted, whereby the IC chip is electrically connected to the substrate.
As prior art of the buildup type multilayer printed wiring board, there are known JP1994-260756A and JP1994-275959A. In both of the publications, a land is formed on a core substrate having through holes filled with resin filler, interlayer insulating layers having via holes formed therein are provided on the both surfaces of the substrate, respectively, a conductor layer is formed by an additive method and the conductor layer is connected to the land, thereby obtaining a high density multilayer wiring board having fine wirings formed thereon.
However, as the frequency of an IC chip is higher, the noise of occurrence of becomes higher. Particularly if the frequency of the IC chip exceeds 3 GHz, the frequency of occurrence of malfunction or error considerably increases. If the frequency exceeds 5 GHz, the IC chip often turns inoperative. Due to this, it cannot perform operations that the computer should do, i.e., cannot perform desired functions and operations such as delay of the recognition of an image, the changeover of a switch and the transmission of data to the outside of the computer.
If the substrate for an IC chip of this type which can not perform the operations is to be subjected to a non-destructive test and to be dissembled, no problems such as short-circuit or opens do not occur to the substrate itself and if the IC chip having a low frequency (particularly less than 1 GHz) is mounted on the substrate, then no malfunction or error occurs to the IC chip.
A high frequency IC chip has enabled high-speed operation while suppressing generation of heat by increasing or decreasing consumption of power intermittently. For example, it consumes electric power of several tens W instantaneously although it usually consumes only several W. According to an estimation, if loop inductance of a printed wiring board is high at the time of this consumption of several tens W, supplied voltage drops thereby leading to malfunction.
The present invention intends to propose an IC chip for high frequency region, particularly, a multi-layer printed wiring board or a packaged board in which malfunction or error never occurs even if 3 GHz is exceeded.